Internetworking techniques for transferring packets between source and target serving gateways

ABSTRACT

Techniques for wireless communications include operating first and second access networks to provide wireless service to wireless devices. The first and second access networks are associated with respective first and second gateways. The first gateway is operated to (1) receive a request for transferring wireless service of a wireless device from the second access network to the first access network and (2) send a message that includes key information to the second gateway based on the request. The second gateway is operated to (1) send session context information to the first gateway in response to the message and (2) forward a data packet associated with the wireless device to the first gateway. The forwarded data packet includes a packet data network identifier (PDN-ID) to identify a packet data network (PDN) associated with a downlink data packet.

PRIORITY CLAIM AND CROSS REFERENCE TO RELATED APPLICATION

This document claims the benefit of the priority of U.S. ProvisionalApplication Ser. No. 61/218,868, filed Jun. 19, 2009 and entitled“Internetworking Techniques for Transferring Packets Between Source andTarget Serving Gateways,” the entire contents of which are incorporatedby reference as part of the disclosure of the this document.

BACKGROUND

This document relates to wireless communications in wirelesscommunication systems.

Wireless communication systems can include a network of one or more basestations to communicate with one or more wireless devices such as amobile device, cell phone, wireless card, mobile station (MS), userequipment (UE), access terminal (AT), or subscriber station (SS). Eachbase station can emit radio signals that carry data such as voice dataand other data content to wireless devices. A base station can bereferred to as an access point (AP) or access network (AN) or can beincluded as part of an access network. Further, a wireless communicationsystem can include one or more access networks to control one or morebase stations.

A wireless device can use one or more different wireless technologiesfor communications. Various examples of wireless technologies includeCode division Multiple Access (CDMA) such as CDMA2000 1x, High RatePacket Data (HRPD), evolved HRPD (eHRPD), Universal MobileTelecommunications System (UMTS), Universal Terrestrial Radio AccessNetwork (UTRAN), evolved UTRAN (E-UTRAN), Long-Term Evolution (LTE), andWorldwide Interoperability for Microwave Access (WiMAX).

SUMMARY

This document describes technologies, among other things, fortransferring packets between source and target serving gateways.

In one aspect, techniques for transferring packets between source andtarget serving gateways can include operating first and second accessnetworks to provide wireless service to wireless devices. The first andsecond access networks can be associated with respective first andsecond gateways. Techniques can include operating the first gateway toreceive a request for transferring wireless service of a wireless devicefrom the second access network to the first access network and send amessage, that includes key information, to the second gateway based onthe request. Key information can include a uplink key to forward uplinkdata packets associated with the wireless device to the first gatewayand a downlink key to forward downlink data packets associated with thewireless device to the first gateway. Techniques can include operatingthe second gateway to send session context information to the firstgateway in response to the message and forward a data packet associatedwith the wireless device to the first gateway. Forwarding the datapacket can include sending one of the keys that corresponds to a type ofthe data packet. Techniques can include operating the first gateway tohandle the forwarded data packet based on the session contextinformation and the key that corresponds to the type of the data packet.Other implementations can include corresponding systems, apparatus, andcomputer programs, configured to perform the actions of the techniques,encoded on computer readable mediums.

These and other aspects can include one or more of the followingfeatures. Operating the second gateway to forward the data packet caninclude including an uplink data packet from the wireless device in aforwarding packet, including the uplink key in the forwarding packet,and sending the forwarding packet to the first gateway. Operating thesecond gateway to forward the data packet can include including asession reference identifier (SR-ID) in the forwarding packet toidentify a user session associated with the wireless device. Sessioncontext information can include information that associates an InternetProtocol (IP) address of the wireless device with the SR-ID. Sessioncontext information can include information that associates multiple IPaddresses of the wireless device with multiple SR-IDs, respectively.

Operating the second gateway to forward the data packet can includeincluding a downlink data packet addressed to the wireless device in aforwarding packet, including the downlink key in the forwarding packet,and sending the forwarding packet to the first gateway. Operating thesecond gateway to forward the data packet can include including a packetdata network identifier (PDN-ID) in the forwarding packet to identify apacket data network (PDN) associated with the downlink data packet.Session context information can include information that associates thePDN-ID with an Access Point Name (APN) and a network address of agateway of the PDN.

A forwarded data packet can include an uplink data packet. Operating thefirst gateway to handle the forwarded data packet can include sendingthe uplink data packet to a packet data network based on receiving theuplink key with the forwarded data packet. A forwarded data packet caninclude a downlink data packet. Operating the first gateway to handlethe forwarded data packet can include sending the downlink data packetto the first access network for delivery to the wireless device based onreceiving the downlink key with the forwarded data packet. Techniquescan include operating the first access network to deliver the downlinkdata packet to the wireless device based on the first access network'sacquirement of the wireless device. In some implementations, first andsecond access networks can communicate with a wireless device based onthe same wireless technology. In some implementations, first and secondaccess networks can communicate with a wireless device based ondifferent wireless technologies.

In another aspect, techniques for transferring packets between sourceand target serving gateways can include operating different accessnetworks to provide wireless service to wireless devices and operating afirst gateway to send a message to a second gateway in response to awireless device's transfer between different access networks. Themessage can include a first key to forward uplink data packets to thefirst gateway and a second key to forward downlink data packets to thefirst gateway. Techniques can include operating the second gateway tosend session context information to the first gateway in response to themessage and to forward uplink and downlink data packets associated withthe wireless device to the first gateway. Forwarding uplink and downlinkdata packets can include including the first key and the second key intorespective uplink and downlink data packet forwarding communications.Techniques can include operating the first gateway to handle forwardeduplink and downlink data packets based on the session contextinformation and respective first and second keys. Techniques can includeoperating the second gateway to include a session reference identifierin an uplink data packet forwarding communication to the first gateway.Techniques can include operating the second gateway to include a PDN-IDin a downlink data packet forwarding communication to the first gateway.Other implementations can include corresponding systems, apparatus, andcomputer programs, configured to perform the actions of the techniques,encoded on computer readable mediums.

In another aspect, techniques, apparatuses, and systems can includemechanisms for transferring user packets between source and targetserving gateways of different networks such as an Evolved High RatePacket Data (eHRPD) network and an Evolved Universal Terrestrial RadioAccess Network (E-UTRAN).

In yet another aspect, systems for wireless communications can include afirst access network to provide wireless service to wireless devices, asecond access network to provide wireless service to wireless devices, afirst gateway, that is communicatively coupled with the first accessnetwork, and a second gateway, that is communicatively coupled with thesecond access network. The first gateway can be configured to receive arequest for transferring wireless service of a wireless device from thesecond access network to the first access network and send a handovermessage that includes key information. Key information can include auplink key to forward uplink data packets associated with the wirelessdevice to the first gateway and a downlink key to forward downlink datapackets associated with the wireless device to the first gateway. Thesecond gateway can be configured to receive the handover message fromthe first gateway, send session context information to the first gatewayin response to the handover message, forward a data packet associatedwith the wireless device to the first gateway. Forwarding the datapacket can include sending one of the keys that corresponds to a type ofthe data packet. The first gateway can be configured to handle theforwarded data packet based on the session context information and thekey that corresponds to the type of the data packet.

The details of one or more implementations are set forth in theaccompanying attachments, the drawings, and the description below. Otherfeatures will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a wireless communication system.

FIG. 2 shows an example of a radio station architecture.

FIG. 3 shows an example of an inter-gateway handover architecture.

FIG. 4 shows an example of a H1 interface control plane protocol stack.

FIG. 5 shows an example of a H2 interface downlink user plane protocolstack.

FIG. 6 shows an example of a H2 interface uplink user plane protocolstack.

FIGS. 7A and 7B show an example of a communication flow for aninter-gateway handover.

FIG. 8A shows an example of operations on a target gateway.

FIG. 8B shows an example of operations on a source gateway.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Various wireless communication system use gateways to route informationbetween different networked endpoints. Some gateways provide wirelessdevices with access to networks such as the Internet. For example, awireless communication system can include multiple gateways to provideInternet Protocol (IP) connectivity and mobility to wireless devices.

This document describes, among other things, systems and techniques fortransferring packets between source and target serving gateways. Thedescribed systems and techniques include interworking mechanisms fortransferring packets between one or more wireless technologies includinginternetworking techniques for Evolved High Rate Packet Data (eHRPD)network and Evolved Universal Terrestrial Radio Access Network(E-UTRAN). The described systems and techniques include methods forsegregating uplink and downlink user packet streams that belong todifferent user sessions active at a wireless device. This documentincludes descriptions of control plane and user plane protocol stacksrelating to packet transferring procedures on multiple interfacesbetween source and target serving gateways.

A wireless communication system can include multiple serving gateways,such as HRPD Serving Gateways (HSGWs), that provide IP edgefunctionalities to one or more UEs. In some system implementations,HSGWs and wireless devices such as UEs can be considered as edgefunctional entities on an eHRPD access part of eHRPD and E-UTRANinterworking networks. A HSGW can interface with a PDN Gateway (P-GW)and Policy and Charging Rules Function (PCRF) functional entities in anEvolved Packet System (EPS) core. In some implementations, a HSGWinterfaces with an Access Network (AN) functional entity such as a HRPDaccess network.

A HSGW can use one or more communication interfaces such as H1 and H2interfaces to perform a handover of packet handling functionality for awireless device. A H1 interface protocol can be used to communicaterouting information associated with a wireless device between gateways.Based on information from the H1 interface, a H2 interface protocol canappend information append to uplink and downlink packets for tunnelingover the H2 interface. In some implementations, a gateway can userouting encapsulating keys for identifying uplink and downlink H2bearers tunnels in forwarding communications. In some implementations, agateway can use identifiers that identify a specific user session on awireless device or a packet data network associated with an IPconnection. The gateway can selectively include one or more of theidentifiers to identify packets belonging to an individual user sessionor packet data network in forwarding communications on uplink ordownlink H2 bearer tunnels.

FIG. 1 shows an example of a wireless communication system. A wirelesscommunication system can include one or more base stations (BSs) 105,107 to provide wireless service to one or more wireless devices 110. Abase station 105, 107 can transmit a signal on a forward link (FL),called a downlink (DL), to one or more wireless devices 110. A wirelessdevice 110 can transmit a signal on a reverse link (RL), called anuplink (UL), to one or more base stations 105, 107. A wirelesscommunication system can include one or more Access Networks (ANs) 125,127 and a data gateway such as a HRPD Serving Gateway (HSGW) 135, 137for each AN 125, 127. In some implementations, ANs 125, 127 includerespectively base stations 105, 107. HSGWs 135, 137 can communicate witha Packet Data Network (PDN) via a PDN Gateway (P-GW) 145 via a network140. HSGWs 135, 137 can communicate with each other via a network 140.In some implementations, a wireless communication system can includemultiple P-GWs to communicate with different PDNs. In someimplementations, a wireless communication system can include a Policyand Charging Rules Function (PCRF).

Different base stations 105, 107 can use different wirelesstechnologies. For example, one base station 105 can use E-UTRANtechnology and a different base station 107 can use eHRPD technology.Various examples of wireless communication systems that can implementthe present techniques and systems include, among others, wirelesscommunication systems based Code division Multiple Access (CDMA) such asCDMA2000 1x, High Rate Packet Data (HRPD), evolved HRPD (eHRPD),Universal Mobile Telecommunications System (UMTS), Universal TerrestrialRadio Access Network (UTRAN), Evolved UTRAN (E-UTRAN), Long-TermEvolution (LTE), and Worldwide Interoperability for Microwave Access(WiMAX). In some implementations, a wireless communication system caninclude multiple networks using different wireless technologies. Forexample, a wireless communication system can include one or morenetworks based on eHRPD and one or more networks based on E-UTRAN.

FIG. 2 shows an example of a radio station architecture. A radio station205 such as a base station or a wireless device can include processorelectronics 210 such as a microprocessor that implements methods such asone or more of the techniques presented in this document. A radiostation 205 can include transceiver electronics 215 to send and/orreceive wireless signals over one or more communication interfaces suchas an antenna 220. A radio station 205 can include other communicationinterfaces for transmitting and receiving data. A radio station 205 caninclude one or more memories configured to store information such asdata and/or instructions.

HSGWs can use one or more communication interfaces to handle thetransferring of packets when a wireless device switches access networks.For example, HSGWs can use an H1 interface for signaling betweengateways and an H2 interface for transferring packets between gateways.In some H1 and H2 interface protocol stack implementations, a HSGWincludes information in uplink and downlink user packet forwardingcommunications to enable tunneling of such user packets over a H2interface. In some H1 and H2 interface protocol stack implementations, aHSGW includes information in uplink and downlink user packet forwardingcommunications to identify user packets as belonging to different usersessions. In some implementations, a target HSGW can send identifierssuch as two Generic Routing Encapsulation (GRE) keys to a source HSGWduring H1 signaling. An identifier such as a key can include multipledigital bits that represent a key value. HSGWs can use uplink anddownlink GRE keys for segregating, respectively, uplink and downlinkuser packet streams. Uplink and downlink GRE keys with S-HSGW and T-HSGWH1 IP addresses can form logical endpoints of uplink and downlink H2tunnels between the source and target HSGW entities.

A HSGW can provide additional traffic segregation. HSGW operations caninclude segregating uplink and downlink user packet streams that belongto different user sessions active on a UE. A HSGW can include additionalinformation such as a session reference identifier (SR-ID) or a PDNidentifier (PDN-ID) to further segregate traffic. In some H1 and H2interface protocol stack implementations, segregating user packetstreams can include adding SR-ID and PDN-ID information in uplink anddownlink user packet communications, respectively.

FIG. 3 shows an example of an inter-gateway handover architecture. Aninter-gateway handover architecture can include communication pathwaysbetween multiple gateways such as HSGWs, to handle handovers betweengateways. An inter-HSGW handover architecture can include differentHSGWs 305, 310 that are configured to enable UE mobility. In thisexample, a Serving AN (S-AN) 315 provides wireless service to a UE andcommunicates with a Source HSGW (S-HSGW) 305 via an A10/A11 connection.The UE can move from the coverage area of the S-AN 315 to the coveragearea of a Target AN (T-AN) 320. Based on the movement, the UE causes aninteraction between a Target-HSGW (T-HSGW) 310, associated with the T-AN320, and the S-HSGW 305 to manage a transfer of IP connectivity.

The UE can have one or more IP connections with one or more networks viaone or more PDN gateways (P-GW) 325. In some implementations, a P-GW 325can tunnel user packets to and from the S-HSGW via a S2a interface. Asthe UE moves from the coverage area of S-AN 315 to the coverage area ofT-AN 320, the A10/A11 connections are established between the T-HSGW 310and the T-AN 320; and the S2a connection is established between theT-HSGW 310 and the P-GW 325.

Wireless communication system can use one or more techniques describedherein to provide an uninterrupted of user packets between the UE andthe P-GW 325 during the transitioning of the UE's over-the-airconnection from the S-AN 315 to the T-AN 320, and during theestablishment of the A10/A11 and the S2a connections at the T-HSGW 310.S-HSGW 305 and the T-HSGW 310 can user a bearer plane interface such asa H2 interface to tunnel user packets between the S-HSGW 305 and theT-HSGW 310 to provide an uninterrupted flow of user packets during suchinter-HSGW handoffs while user sessions at the UE are in the activestate. In some implementations, the H2 tunnel is established aftersession context information has been exchanged between the S-HSGW 305and the T-HSGW 310 via a control plane interface such as a H1 interface.

As multiple user sessions may be active at an UE with one or more P-GWs,techniques are disclosed herein to unambiguously identify uplink anddownlink user packets tunneled over the H2 interface that belong todifferent user sessions. For example, a UE can use a first IP addressfor communications via a first P-GW and can use a second IP address forcommunications via a second P-GW. One or more of the techniques includeincluding information such as a GRE keys for identifying UL and DL H2bearers tunnels and SR-ID and the PDN-ID for identifying packetsbelonging to the individual user sessions on the UL and DL H2 bearertunnels respectively.

In some implementations, when the UE moves to a coverage area of a newAN and the HRPD session is successfully transferred from the S-AN to theT-AN, the T-AN may select a new HSGW for serving the UE sessions. Forexample, if the S-HSGW is not reachable from the T-AN, then the T-ANselects a new T-HSGW for the UE sessions. The T-AN can provide S-HSGW H1interface IP address information to the T-HSGW during an A10 connectionestablishment procedure. In some implementations, the T-AN receivesS-HSGW H1 IP Address information from the S-AN based on proceduresperformed over the A16/A13 interfaces. Based on the S-HSGW IP address,the T-HSGW initiates H1 interface signaling with the S-HSGW requestingthe later for the context information for active user sessionsassociated with the UE.

H1 interface signaling procedures between the S-HSGW and the T-HSGW canbe based on the reactive handover procedures such as those for FastHandovers for Proxy Mobile IPv6. The H2 interface can support “RFC 2784:Generic Routing Encapsulation (GRE).” The H2 interface can support GREkey field extensions based on “RFC 2890: Key and Sequence NumberExtensions to GRE.”

In some implementations, the key field value of a GRE packet header canidentify a UL or DL traffic flow including UL or DL user data packetsfor a given UE. For DL traffic, the H2 interface can carry user IPpackets, such as IPv4 or IPv6 packets, identified by the associatedPDN-ID, over an underlying transport network. For UL traffic, the H2interface can carry PDN-Mux or dedicated service connection trafficreceived over the A10 connection(s), identified by the associatedservice connection SR-ID, over an underlying transport network.

FIG. 4 shows an example of a H1 interface control plane protocol stack.In this example, a S-HSGW 405 and a T-HSGW 410 exchange signalinginformation over a H1 interface control plane protocol stack. An H1interface control plane protocol stack can include a physical layer(L1), a data link layer (L2), a network layer (L3) such as IPv4 or IPv6,and a H1 signaling layer.

FIG. 5 shows an example of a H2 interface downlink user plane protocolstack. In this example, a S-HSGW 505 forwards downlink data packets fora UE to a T-HSGW 510 using a downlink user plane protocol stack such asa H2 interface downlink user plane protocol stack. A H2 interfacedownlink user plane protocol stack can include a physical layer (L1), adata link layer (L2), a network layer (L3) such as IPv4 or IPv6, a GRElayer, a layer that identifies a PDN-ID associated with a downlink datapacket, and a layer for communicating the contents of the downlink datapacket, e.g., IPv4 or IPv6 traffic addressed to the UE. In someimplementations, each user IPv4/IPv6 packet identified by the associatedPDN-ID is sent over the transport network between the S-HSGW and theT-HSGW using the DL GRE key assigned via H1 signaling.

FIG. 6 shows an example of a H2 interface uplink user plane protocolstack. In this example, a S-HSGW 605 forwards uplink data packets from aUE to a T-HSGW 610 using uplink user plane protocol stack such as a H2interface uplink user plane protocol stack. A H2 interface uplink userplane protocol stack can include a physical layer (L1), a data linklayer (L2), a network layer (L3) such as IPv4 or IPv6, a GRE layer, alayer that identifies a SR-ID associated with a uplink data packet, anda layer for communicating the contents of the uplink data packet, e.g.,IPv4 or IPv6 traffic sent from the UE. In some implementations, A10payload received over the service connection(s) identified by theassociated service connection SR-ID is sent over the transport networkbetween the S-HSGW and the T-HSGW using the UL GRE key assigned via H1signaling.

As split between two drawing sheets, FIGS. 7A and 7B show an example ofa communication flow for an inter-gateway handover. In this example,when a UE connects to a T-AN, the UE requires a new HSGW, e.g., T-HSGW,for continued IP connectivity. As a result, a A10/A11 connection isrequired with the newly selected T-HSGW. During the handover procedure,S-HSGW and T-HSGW can use a H1 signaling interface to transferinformation relating to one or more user sessions associated with theUE. Such information can include one or more UE IP addresses associatedwith one or more user sessions, one or more Traffic Flow Templates(TFTs), and PPP state. S-HSGW and T-HSGW can use a H2 bearer interfacefor UE UL and DL packet transfers from the S-HSGW to the T-HSGW.

At 700, the UE has an active session with the P-GW via the source AN(S-AN) and source HSGW (S-HSGW). For the purpose of this example callflow, only a single user session is shown between the UE and the P-GW.The UE may have several active sessions with one or several P-GWs.

At 701, an end-to-end path between the UE and the correspondent node isestablished and the UE can send/receive packets to/from the network viathe S-AN, S-HSGW and P-GW.

At 702, the UE reports pilot strength of the neighboring ANs to theserving AN (S-AN). The S-AN determines the need for handing off the UEto the target AN (T-AN).

At 703, the S-AN performs A16-Session Information Transfer procedureswith the selected T-AN over the A16 interface. Via such signaling, usersession information is passed from the S-AN to the T-AN. User sessioninformation can include SR-IDs for one or more active user sessions,Session State Information Records, and the address of the S-HSGW.

At 704, the T-AN performs A11 Registration Request (RRQ) and A11Registration Response (RRP) procedures with the T-HSGW to signal thehandoff. A10/A11 message exchange from the T-AN includes the S-HSGW IPaddress, MSID of the UE, and sets the A10 connections for the UE, etc.

At 705 a, triggered by A10/A11 signaling (e.g., at 704), the T-HSGWsends a Handover Initiate (HI) message to the S-HSGW to request the usersession context, subscription context, etc. A Handover Initiate messagecan include a MSID of the UE and two or more GRE Keys. In someimplementations, a Handover Initiate message can include two GRE Keysthat the T-HSGW uses for the two uni-directional tunnel(s) betweenS-HSGW and T-HSGW for packet transfer. One GRE Key corresponds to theGRE tunnel for forwarding the UL packets to the T-HSGW and the other GREKey corresponds to the GRE tunnel for forwarding the DL packets to theT-HSGW.

At 705 b, the S-HSGW sends a Handover Ack (HAck) message to the T-HSGWwith the session context information, TFTs etc. As an example, for eachestablished user session (PDN connection), the HAck message includessession context information. Various examples of session contextinformation includes one or more of: a mobile node network addressidentifier (MN-NAI), one or more IPv4/IPv6 addresses or prefixesassociated with the UE, one or more Evolved Packet System (EPS) AccessPoint Names (APNs), one or more TFTs, one or more P-GW IP addresses,policy context, compression context, and PPP state. Such session contextinformation can enable the T-HSGW to take over uninterrupted processingof user packets during the handover. Session context information caninclude indicia of relationships of each PDN-ID with APN, P-GW address,and the GRE key for UL traffic to the P-GW over S2a interface. Suchinformation can enable uninterrupted processing of user packets betweenthe T-HSGW and one or more P-GWs. In some implementations, a HAckmessage can include information arranged in a tag-length-value (TLV)format.

At 706 a, user packets from the correspondent node continue to reach theS-HSGW via the P-GW. The S-HSGW extracts the DL packets over the S2atunnel from the P-GW and forwards these packets to the T-HSGW over theDL H2 GRE tunnel by using the received DL GRE Key (e.g, DL GRE Keyreceived at 705 a).

At 706 b, the PDN-ID corresponding to this user session can be added infront of each DL packet and the packet is sent to the T-HSGW as receivedfrom the P-GW.

At 706 c, the T-HSGW performs packet processing based on the sessioncontext information received (e.g., session context information receivedat 705 b) and the PDN-ID embedded before each of these DL packets, andforwards them to the T-AN. These packets are buffered there until the UEshifts the air-interface connection to the T-AN.

At 707, responsive to the HAck message, the T-HSGW sends a proxy-MobileIP Proxy Binding Update (PBU) message to the P-GW to update the bindingcache entry (BCE) for the UE with T-HSGW's IP address as the new S2atunnel end-point.

At 708 a, the UL packets, including any control signaling packets (e.g,RSVP, DHCP etc.) that the UE is still sending via the S-AN are receivedat the S-HSGW.

At 708 b, these packets are forwarded by the S-HSGW to the T-HSGW overthe UL GRE tunnel over the H2 interface using the UL GRE Key. The S-HSGWforwards the payload of the GRE packet it receives over the A10 tunnelsto the H2 GRE tunnel. In some implementations, a S-HSGW adds thecorresponding SR-ID in front of each A10 payload packet and places thisas the payload of a communication on the UL H2 GRE tunnel.

At 708 c, the T-HSGW performs packet processing for these UL packetssuch as processing for HDLC and PPP de-framing. The session contextinformation and the SR-ID appended before each UL packet allows theT-HSGW to correlate each UL packet with the appropriate A10 connectionand hence to the correct user session. The T-HSGW forwards user packetsto the P-GW over a S2a interface.

At 709 a, the P-GW updates its BCE, switches the data path to the T-HSGWand returns a proxy-Mobile IP Proxy Binding Ack (PBA) to the T-HSGW toindicate successful operation. The P-GW can perform a RegistrationRevocation procedure with the S-HSGW, such as sending an indication of abinding revocation.

At 709 b, the P-GW sends a Binding Revocation Indication (BRI), such asa PMIPv6 Binding Revocation, to the S-HSGW and receives anacknowledgement.

At 710, now that the BCE is updated and the packet-path is switched, theDL packets from the P-GW start flowing to the T-HSGW. The T-HSGWforwards them to the T-AN. The T-AN buffers them until they can bedelivered to the UE (after the air-interface connection is switched tothe T-AN).

At 711 a, the S-AN sends a Traffic Channel Assignment message toinstruct the UE to switch to the new AN (T-AN). The S-AN can send such amessage based on performing A16-Session Information Transfer procedures.

At 711 b, the T-AN acquires the UE over the air-interface connection.The T-AN can now transmit buffered packets to the UE.

At 712, based on receiving the HAck message, the T-HSGW interacts withthe PCRF, via a Gxa interface, to set up the policy associated with thebearer(s) of the UE.

At 713, the T-AN starts emptying its buffer and as the T-AN delivers thebuffered DL packets to the UE.

At 714, based on acquiring the UE, the T-AN performs A11-RegistrationRequest/Response message exchange with the T-HSGW which includes anActive Start Airlink record indication. This is to indicate to theT-HSGW that the path to the UE over the air-interface connection is nowestablished via the T-AN.

At 715, at this time, both UL and DL traffic for the UE are goingthrough the target system. After being acquired by the T-AN (e.g., at711 b), the UE can begin to send UL packets via the T-AN. After the P-GWswitches the data path to the T-HSGW, the T-HSGW receives DL packetsfrom the P-GW and forwards the DL packets to the T-AN.

At 716 a, after the binding revocation (e.g., at 709 b) and after theT-HSGW detects that there has been no packets for a configurable periodof time over the H2 tunnel, the T-HSGW sends a H1 message to tear downthe H2 tunnels between the S-HSGW and T-HSGW.

At 716 b, the S-HSGW sends a HAck message to acknowledge successfulteardown of the H2 tunnel(s). The S-HSGW deletes all context for the UE.

At 717, based on information in the PBU, the P-GW interacts with thePCRF (via the Gx interface) to setup the policy associated with the newbearer(s) via the target system. This can happen in parallel with theS2a tunnel set up.

At 718, the S-HSGW performs a Session Termination Request/Answerprocedure with the HSS/AAA to update its state information.

At 719, based on acquiring the UE and being assured that access to thesystem by the UE would be directed to the T-AN, the T-AN performs anA16-Session Release procedure with the S-AN. This message exchangeindicates that the session is now under control of the T-AN. The S-ANcan terminate its connection with the S-HSGW and can purge the sessionassociated with the UE.

At 720, After sending the HAck message to acknowledge successfulteardown of the H2 tunnel(s), the S-HSGW performs A11 connection releaseprocedures with the S-AN to request tearing down the A10 connection withthe S-AN.

FIG. 8A shows an example of operations on a target gateway. A targetgateway, such as a T-HSGW, can receive a request for transferringwireless service of a wireless device (805). The target gateway can senda message to a source gateway based on the request (810). The messagecan include key information. Key information can include a uplink key toforward uplink data packets associated with the wireless device to thetarget gateway. Key information can include a downlink key to forwarddownlink data packets associated with the wireless device to the targetgateway. The target gateway can receive data including session contextinformation and forwarded data packets (815). Receiving a forwarded datapacket can include receiving a data packet with an attached key thatcorresponds to a type of the data packet, e.g., uplink data packet ordownlink data packet. In some implementations, the target gateway canreceive a communication that includes multiple forwarded data packetswith multiple attached keys. The target gateway can handle forwardeddata packets based on the session context information and attached oneor more keys (820).

FIG. 8B shows an example of operations on a source gateway. A sourcegateway, such as a S-HSGW, can receive a message from a target gateway(830). The source gateway can send session context informationassociated with the wireless device to the target gateway in response tothe message (840). The source gateway can forward data packetsassociated with the wireless device to the target gateway (850).Forwarding data packets can include attaching a key that corresponds toa type of a data packet.

Forwarding a data packet can include including an uplink data packetfrom the wireless device in a forwarding packet, including the uplinkkey in the forwarding packet; and sending the forwarding packet to thetarget gateway. In some implementations, forwarding a data packetincludes including a SR-ID in the forwarding packet to identify a usersession associated with the wireless device.

Forwarding a data packet can include including a downlink data packetaddressed to the wireless device in a forwarding packet, including thedownlink key in the forwarding packet; and sending the forwarding packetto the target gateway. In some implementations, forwarding a data packetincludes including a PDN-ID in the forwarding packet to identify a PDNassociated with the downlink data packet.

The disclosed and other embodiments and the functional operationsdescribed in this document can be implemented in digital electroniccircuitry, or in computer software, firmware, or hardware, including thestructures disclosed in this document and their structural equivalents,or in combinations of one or more of them. The disclosed and otherembodiments can be implemented as one or more computer program products,i.e., one or more modules of computer program instructions encoded on acomputer readable medium for execution by, or to control the operationof, data processing apparatus. The computer readable medium can be amachine-readable storage device, a machine-readable storage substrate, amemory device, a composition of matter effecting a machine-readablepropagated signal, or a combination of one or more them. The term “dataprocessing apparatus” encompasses all apparatus, devices, and machinesfor processing data, including by way of example a programmableprocessor, a computer, or multiple processors or computers. Theapparatus can include, in addition to hardware, code that creates anexecution environment for the computer program in question, e.g., codethat constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, or a combination of one or moreof them. A propagated signal is an artificially generated signal, e.g.,a machine-generated electrical, optical, or electromagnetic signal, thatis generated to encode information for transmission to suitable receiverapparatus.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this document can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto optical disks, or optical disks. However, a computerneed not have such devices. Computer readable media suitable for storingcomputer program instructions and data include all forms of non volatilememory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto optical disks; and CD ROM and DVD-ROM disks. The processor andthe memory can be supplemented by, or incorporated in, special purposelogic circuitry.

While this document contains many specifics, these should not beconstrued as limitations on the scope of an invention that is claimed orof what may be claimed, but rather as descriptions of features specificto particular embodiments. Certain features that are described in thisdocument in the context of separate embodiments can also be implementedin combination in a single embodiment. Conversely, various features thatare described in the context of a single embodiment can also beimplemented in multiple embodiments separately or in any suitablesub-combination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asub-combination or a variation of a sub-combination. Similarly, whileoperations are depicted in the drawings in a particular order, thisshould not be understood as requiring that such operations be performedin the particular order shown or in sequential order, or that allillustrated operations be performed, to achieve desirable results.

Only a few examples and implementations are disclosed. Variations,modifications, and enhancements to the described examples andimplementations and other implementations can be made based on what isdisclosed.

1-26. (canceled)
 27. A method for wireless communications, comprising:receiving a request at a target gateway operating in a target accessnetwork for transferring wireless service of a wireless device from asource access network to the target access network; sending, from thetarget gateway, a handover initiate message comprising a downlink key toa source gateway operating in the source access network; receiving, atthe target gateway, an acknowledgement message comprising protocol datanetwork identification (PDN-ID) associated with an established usersession; receiving, at the target gateway, subsequent to the receivingthe acknowledgement message, a forwarding packet for the wirelessdevice, the forwarding packet using the downlink key and the sessioncontext information; and forwarding the downlink packet to the targetaccess network.
 28. The method recited in claim 27, wherein the sessioncontext information includes information that associates the PDN-ID withan Access Point Name and a network address of a gateway of the PDN. 29.The method recited in claim 27, wherein the source access network andthe target access network are based on the same wireless technology. 30.The method recited in claim 27, wherein the source access network andthe target access network are based on different wireless technologies.31. A target access server operable in a target access network,configured to: receive a request to transfer wireless service of awireless device from a source access network to the target accessnetwork; send a handover initiate message comprising a downlink key to asource gateway operating in the source access network; receive anacknowledgement message comprising protocol data network identification(PDN-ID) associated with an established user session; receive,subsequent to the receiving the acknowledgement message, a forwardingpacket for the wireless device, the forwarding packet using the downlinkkey and the session context information; and forward the downlink packetto the target access network.
 32. The server recited in claim 31,wherein the session context information includes information thatassociates the PDN-ID with an Access Point Name and a network address ofa gateway of the PDN.
 33. The server recited in claim 31, wherein thesource access network and the target access network are based on thesame wireless technology.
 34. The server recited in claim 31, whereinthe source access network and the target access network are based ondifferent wireless technologies.
 35. A method for wirelesscommunications, comprising: receiving, at a source gateway operating ina source access network, a handover initiate message comprising adownlink key from a target gateway operating in a target access network;transmitting, to the target gateway, an acknowledgement messagecomprising protocol data network identification (PDN-ID) for anestablished user session; and transmitting, to the target gateway,subsequent to the transmitting the acknowledgement message, a forwardingpacket for a wireless device, the forwarding packet using the downlinkkey and the PDN-ID.
 36. The method recited in claim 35, wherein thesession context information includes information that associates thePDN-ID with an Access Point Name and a network address of a gateway ofthe PDN.
 37. The method recited in claim 35, wherein the source accessnetwork and the target access network are based on the same wirelesstechnology.
 38. The method recited in claim 35, wherein the sourceaccess network and the target access network are based on differentwireless technologies.
 39. A gateway server operable in a source accessnetwork, configure to: receive a handover initiate message comprising adownlink key from a target gateway operating in a target access network;transmit, to the target gateway, an acknowledgement message comprisingprotocol data network identification (PDN-ID) for an established usersession; and transmit, to the target gateway, subsequent to thetransmitting the acknowledgement message, a forwarding packet for awireless device, the forwarding packet using the downlink key and thePDN-ID.
 40. The server recited in claim 39, wherein the session contextinformation includes information that associates the PDN-ID with anAccess Point Name and a network address of a gateway of the PDN.
 41. Theserver recited in claim 39, wherein the source access network and thetarget access network are based on the same wireless technology.
 42. Theserver recited in claim 39, wherein the source access network and thetarget access network are based on different wireless technologies. 43.A method for wireless communications, comprising: receiving a request ata target gateway operating in a target access network for transferringwireless service of a wireless device from a source access network tothe target access network; sending, from the target gateway, a handoverinitiate message comprising an uplink key to a source gateway operatingin the source access network; receiving, at the target gateway, usersession information including session reference identifiers (SR-IDs)associated with multiple Internet Protocol (IP) addresses of thewireless device; receiving, at the target gateway, subsequent to thereceiving the acknowledgement message, a forwarding packet for thewireless device, the forwarding packet using the uplink key and one ofthe SR-IDs; and forwarding the uplink packet to a gateway server. 44.The method recited in claim 43, wherein the source access network andthe target access network are based on the same wireless technology. 45.The method recited in claim 43, wherein the source access network andthe target access network are based on different wireless technologies.46. A gateway device operable in a target access network, configured to:receive a request operating in the target access network fortransferring wireless service of a wireless device from a source accessnetwork to the target access network; Send a handover initiate messagecomprising an uplink key to a source gateway operating in the sourceaccess network; receive user session information including sessionreference identifiers (SR-IDs) associated with multiple InternetProtocol (IP) addresses of the wireless device; receive, subsequent tothe receiving the acknowledgement message, a forwarding packet for thewireless device, the forwarding packet using the uplink key and one ofthe SR-IDs; and forwarding the uplink packet to a gateway server. 47.The server recited in claim 46, wherein the source access network andthe target access network are based on the same wireless technology. 48.The server recited in claim 46, wherein the source access network andthe target access network are based on different wireless technologies.49. A method for wireless communications, comprising: receiving, at asource gateway operating in a source access network, a handover initiatemessage comprising an uplink key from a target gateway operating in atarget access network; transmitting, to the target gateway, informationincluding session reference identifiers (SR-IDs) associated withmultiple Internet Protocol (IP) addresses of a wireless device; andtransmitting, to the target gateway, subsequent to the transmittinginformation, a forwarding packet for the wireless device, the forwardingpacket using the uplink key and one of the SR-IDs.
 50. The methodrecited in claim 49, wherein the source access network and the targetaccess network are based on the same wireless technology.
 51. The methodrecited in claim 49, wherein the source access network and the targetaccess network are based on different wireless technologies.
 52. Agateway server operable in a source access network, configured to:receive a handover initiate message comprising an uplink key from atarget gateway operating in a target access network; transmit, to thetarget gateway, information including session reference identifiers(SR-IDs) associated with multiple Internet Protocol (IP) addresses of awireless device; and transmitting, to the target gateway, subsequent tothe transmitting information, a forwarding packet for the wirelessdevice, the forwarding packet using the uplink key and one of theSR-IDs.
 53. The server recited in claim 52, wherein the source accessnetwork and the target access network are based on the same wirelesstechnology.
 54. The server recited in claim 52, wherein the sourceaccess network and the target access network are based on differentwireless technologies.